A magnet switch and a starter using same

Abstract: Disclosed is a starter which prevents a magnetic flux change of field device in a d.c. motor against a magnetic field produced by a battery cable and also prevents contact between the battery cable and the d.c. motor when a vehicle vibrates. In the periphery of a magnet switch cover (3c), a pair of a first fixed contact (27) and a second fixed contact (28) are disposed opposing to a moving contact (23). The first fixed contact (27) is conducted to a battery connecting terminal (27a) which connects to a battery cable (30). The switch cover (3c) covers a opening of the switch casing (1a). A motor cover (3d) covers an opening of a motor casing (1b) disposed in parallel with a magnet switch (18). On a mounting surface (3b) of the battery cable connecting terminal (27a) in the switch cover (3c), a washer (29) protrudes from the back end portion (3a) of the motor cover (3d) in the axial direction.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention: The present invention relates to a magnet switch and a starter housing of an internal combustion engine, according to the preamble of claim 1 and to a starter according to the preamble of claim 4. (JP 55-45893) 2. Related Art: In a starter having a conventional magnet switch, the magnet switch is disposed on the upper portion of a d.c. motor and is fixed by a screw. A fixed seat surface of a battery connecting terminal is located inside of the d.c. motor axial to its back end portion. The cap of the magnet switch is disposed having a stage between the fixed seat surface and a fixed seat surface of the d.c. motor input terminal. These fixed seat surfaces are caulked via a washer with the battery connecting terminal for the fixed seat surface and the d.c. motor input terminal for the fixed seat surface. This publication also discloses a structure which can install a battery cable at any place around the magnet switch as the fixed seat surface of the battery cable connecting terminal protrudes more than the fixed seat surface of the d.c. motor input terminal. However, as for a starter having magnet switch as described above, especially a low torque speed reduction type starter employing a magnet as a field device for the d.c. motor, a battery cable is wired in the upper portion of d.c. motor because a fixed seat portion of the battery connecting terminal is located on the interior side of the back end portion of d.c. motor. In this state, when an electric current is applied to the battery cable, a magnetic field is produced. This magnetic field changes the magnetic flux of the magnet in the field device, thereby causing a phenomenon where the starter efficiency deteriorates to the same degree as the magnetic flux is changed. In addition, although such a starter can have the battery cable installed at any direction around the periphery of the battery connecting terminal, as a battery cable is disposed in the upper portion of a d.c. motor, when a vehicle vibrates, the battery cable scrapes the d.c. motor so that an insulating coating of the battery cable may peel off. The US patent 5 003 206 discloses a solenoid for energizing a starter motor wherein a disc for connecting stationary contacts initially contacts with a first stationary contact and later with two other contacts in response to the solenoid which is energized. The bolt for connecting a stationary contact to a source of electrical energy is disposed in such a manner that an influence between battery cable and housing of the motor is not excluded. The US patent publication 4 695 735 discloses a starter drive for an internal combustion engine wherein the start drive is mounted within a starter-housing on the same axis as a starter motor. A first terminal contact which provides the connection with the battery protrudes from the back end of the starter housing in such a manner that the battery cable is able to contact the starter housing. The US patent publication 4 631 434 provides a starter in which a magnet switch is arranged in parallel with the starter motor. An axial side end of the starter housing opposite to the side, on which a starter pinion is provided, protrudes from the connecting seat surface of a contact of the magnet switch which is connected to a battery. Thus contact between the battery cable and the motor can occur. Furthermore, the magnetic field of the battery cable is able to change the magnetic flux in the motor. The object of the Japanese Utility Model Laid-open publication No. 60-21561 is to provide a dust, water and sound-proof starter structure. For this object, a case with sound absorbing material is provided to surround a starter. Since an input terminal of a magnet switch is covered by the case, an additional terminal for connection with a battery is used separately from the input terminal. If no cover nor sound absorbing material is used, the additional terminal will not be necessary. Document JP-Y2 55-45893, which constitutes the next coming prior art, discloses a starter having a starter motor and a magnet switch. The magnet switch has a switch cover at which a battery connecting termimal and a motor connecting terminal are provided. These terminals are provided in direction of the center axis of the starter on the same level. Two nuts between which a battery cable is attached are screwed on the battery connecting terminal. Though the battery cable has in direction of the center axis of the starter a predetermined distance to the motor casing a contact between the battery cable and the nuts of the terminals which are disposed at the d.c. motor may occur. Furthermore, changes in the magnetic flux of a field device of a d.c. motor against an interfering magnetic field are produced when an electric current is applied to the battery cable. SUMMARY OF THE INVENTION The present invention intends to provide a magnet switch and a starter housing for a starter which prevents changes in the magnetic flux of a field device in a d.c. motor against an interfering magnetic field produced when an electric current is applied to a battery cable. Also, the present invention intends to provide a starter which prevents contact between a battery cable and a d.c. motor even when the vehicle vibrates. This object is solved by a magnet switch and a starter housing according to claim 1 and a starter according to claim 4. Further embodiments are disclosed in the subclaims. According to the present invention, a magnet switch of a starter includes a fixed contact and a moving contact which interrupt carrying current to a starter motor for starting an internal combustion engine. The magnet switch further includes a battery connecting terminal electrically connected to the fixed contact and disposed on the back end portion of a casing in the magnet switch. The battery connecting terminal protrudes towards the exterior of the casing. A connecting seat surface of the battery connecting terminal is located in a more outwards direction than the back end portion of casing of the starter motor. According to the present invention, as a connecting seat surface of a battery connecting terminal installed in a battery cable in a magnet switch and a back end portion of a casing of the magnet switch are located in a more outward direction than a back end portion of the casing in a motor, a distance between the battery cable and a motor field device can be long, thereby preventing magnetic flux changes of field device against an interfering magnetic field produced when an electric current is applied to the battery cable. Further, deterioration of the starter output is prevented. Further, a battery cable can be prevented from being in contact with a housing of the d.c. motor even if a vehicle vibrates because a terminal of the battery cable can be installed in any direction from the periphery of the battery connecting terminal and the battery cable is not disposed on the motor. Further, a washer seat surface in a magnet switch cover installed on a battery cable protrude in the direction axial to the back end portion of a motor cover, thereby setting a distance between the washer seat surface and the back end portion of motor cover long, favorably preventing a magnetic flux change in a motor field device without deteriorating a starter output, and further easily preventing contact between the battery cable and a casing of d.c. motor even if a vehicle vibrates. Furthermore, as a magnet switch casing and a motor casing are integrated with magnetic material and a magnet switch cover and a motor cover are also integrated with heat resisting resin material, the number of parts can be reduced, and the structure of starter can be simplified and downsized. BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features, and characteristics of the present invention, along with the function of the related parts, will be better understood by study of the following detailed description, appended claims, and drawings. In the drawings: Fig. 1 is a cross-sectional view of a starter according to the first embodiment of the present invention; Fig. 2 is a front view of a starter casing shown in Fig. 1; Fig. 3 is a schematic view showing a state of installing a battery cable to the starter of Fig. 1; and Fig. 4 is a partial side view showing second embodiment of the present invention. DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS A starter of the present invention will be described in detail below with reference to the accompanying drawings. Fig. 1 is a cross-sectional view showing the first embodiment of the present invention, Fig. 2 is a front view of a starter casing, and Fig. 3 is a schematic view showing a state of mounting a battery cable. Starter casing 1 integrated with a magnetic material comprises cylindrical magnet switch casing 1a which contains magnet switch 18 and cylindrical motor casing 1b which contains rotary-driven armature 2. Starter cover 3 formed of heat resistant resin material includes switch cover 3c which covers an opening portion of magnet switch casing 1a and motor cover 3d which covers an opening portion of motor casing 1b. Starter cover 3 is fixed to casing 1 axially by bolts 33 (Fig. 3). In addition, motor 34 includes motor casing 1b and armature 2 disposed in motor cover 3d as will be described later. Magnet 32 constituting a field device is disposed in the peripheral portion of motor casing 1b, and armature 2 is disposed within the periphery of magnet 32. Armature 2 is composed of armature core 2a, an armature coil (not shown) which is embedded in the outer peripheral portion of armature core 2a and armature shaft 2b press fitted in armature core 2a. One side (back side) of armature shaft 2b is rotatably supported by bearing 3e of starter cover 3, and the other side (front side) of armature shaft 2b is rotatably supported by bearing 6 disposed in a convex portion of rotation output shaft 5, described below. In addition, commutator 2c is fixed to one side of the armature shaft 2b. In the outer peripheral portion of commutator 2c, brush 4 having pigtail 4a fixed to starter cover 3 is rotatably disposed by screw 26 via a second fixed contact 28. Sun gear 2d is formed on the outer periphery on the other side of armature shaft 2b. Still further, in this side of armature shaft 2b, rotation output shaft 5 is disposed on the same axis to or coaxially with armature shaft 2b. One edge of the rotation output shaft 5 is rotatably supported by bearing 12b mounted on center bearing 12 which is fixed to housing 8, and the other edge of the rotation output shaft 5 is rotatably supported by bearing 7 in housing 8. Flange-shaped overhang 5a is formed on one edge of rotation output shaft 5 protruding in the outer peripheral direction. The overhang 5a has a plurality of through holes 5b in the peripheral direction. Pins 10 are disposed engaging through holes 5b and rotatably supporting planetary gears 11 thereon via bearings 9. Planetary gears 11 engage the outer periphery of aforementioned sun gear 2d. Furthermore, in the outer periphery of flange-shaped overhang 5a, internal gear 12a is disposed in the inner peripheral surface. Sun gear 2d, planetary gears 11 and internal gear 12 compose a speed reduction mechanism. On the side of rotation output shaft 5 opposite to housing 8 (i.e., at the left bottom portion in the figure), a torque converter 13 is installed along with an automatic transmission (not shown) disposed on a vehicle side. Overrunning clutch 15, having pinion gear 15a engageable with ring gear 14 disposed in torque converter 13, is engaged with a helical spline (not shown) of rotation output shaft 5. Change speed lever 16 engages with annular member 17. One end of change speed lever 16 is installed on overrunning clutch 15, and the other end thereof is engaged with joint member 19a of plunger 19. Rotation output shaft 5 is covered by housing 8. The starter casing 1 is fixed between the housing 8 and starter cover 3 via a through bolt 33 which is shown in Fig. 3. In the inner peripheral portion of magnet switch casing 1a, plunger 19 is disposed and set movably in an axial direction of a cylindrical sleeve 20 composed of non-magnetic material, such as brass, as if plunger 19 is guided by sleeve 20. Exciting coil 25 is disposed on the periphery of sleeve 20. In the edge portion of sleeve 20, stationary core 21 made of magnetic material is inserted. In the middle portion of stationary core 21, an aperture is formed, through which drive shaft 22 penetrates. Drive shaft 22 protrudes from end face of plunger 19. Moving contact 23 is disposed opposing the side face of plunger in stationary core 21 so that moving contact 23 is integrally combined with drive shaft 22. Compression spring 24 is disposed between plunger 19 and stationary core 21 to keep plunger 19 away from stationary core 21 normally. The edge portion of stationary core 21 is covered with starter cover 3, in which first fixed contact 27 and second fixed contact 28 are disposed opposing moving contact 23. First fixed contact 27 includes battery connecting terminal 27a which is fit into starter cover 3. Washer 29 is in contact with mounting seat surface 3b of starter cover 3 and engaged with battery connecting terminal 27a. Battery connecting terminal 27a is connected to battery cable 30 via nut 31. Further, washer seat surface 29a of washer 29 on mounting seat surface 3b of starter cover 3 protrudes from rear end portion 3a of starter cover 3 by length L in the axial direction. The operation of the embodiment of the present invention described above will be set forth below. When a key switch (not shown) is turned ON, an electric current is carried to exciting coil 25 via battery connecting terminal 27a towards which plunger 19 is attracted so as to come into contact therewith. Change speed lever 16 engaged with joint 19a is rotated clockwise. By this rotation of change speed lever 16, overrunning clutch 15 is moved forward guided by the helical spline (not shown) along the rotation output shaft 5. Moving contact 23 contacts first fixed contact 27 and second fixed contact 28, and the electric current is carried to armature 2 via brush 4. The armature 2 finally rotates by means of an exciting magnetic flux of magnet 32. This rotation of armature 2 turns planetary gears 11 engaged with the internal gear 12 and sun gear 5a on armature shaft 2b so as to rotate overhang 5b and rotation output shaft 5 in a reduced rotation speed. This reduced rotation is transmitted via the helical spline (not shown) to overrunning clutch 15, which slides over rotation output shaft 5. Pinion gear 15a engages with ring gear 14, ring gear 14 rotates, and then the engine starts. After starting the engine, when pinion gear 15a is counter-rotated by ring gear 14, the rotation transmitted from ring gear 14 is not transmitted due to the operation of overrunning clutch 15, thereby preventing armature 2 from over-running. When the key switch is turned OFF for completion of the starting of the engine, electrical current supply to magnet switch 18 is stopped, and then plunger 19 springs back to its initial position by force from spring 24. Thus, moving contact 23, first fixed contact 27, and second fixed contact 28 are opened, feeding electrical current to armature 2 is stopped, and then pinion gear 15a is uncoupled from ring gear 14. Fig. 4 shows the second embodiment of the present invention. This embodiment separates motor cover 3d containing armature from magnet switch cover 3c containing a magnet switch. Washer 29 is disposed on mounting seat surface 3b of the magnet switch cover 3c and is engaged with battery connecting terminal 27a. Washer seat surface 29a, which contacts a battery cable, protrudes from back end portion 3a of starter cover 3 by length L in the axial direction. According to the embodiment, as seat bearing surface 29a is in contact with battery cable 30 and magnet switch cover 3c protrudes from back end portion 3a of motor cover 3d by length L in the axial direction, the distance between battery cable 30 and the field device, i.e. magnet 32, can be long, thereby preventing the changes in magnetic flux of the field device, i.e. demagnetization, and deterioration of rectification and also preventing deterioration of starter output. In addition, as battery cable 30 can be installed in any direction of the periphery of battery connecting terminal 27a as shown in Fig. 3 and is not disposed on motor 34, battery cable 30 can be prevented from contacting with motor 34 even if a vehicle is subjected to vibration. Motor cover 3d and magnet switch cover 3c may be integrated, thereby reducing the number of parts, and both simplifying and reducing in size the structure of the starter. Also in the embodiment of the present invention shown in Fig. 1, it is possible to move a magnet switch 18 backward to line up the back end portion of magnet switch 18 with the back end of motor 34, thereby becoming integral with starter cover 3, connecting with brush 4 from second fixed contact 28 directly to inside of the magnet switch 18, and removing a motor lead wire. This prevents poor operation of the starter due to rusting. Further, in each of the embodiments of the present invention mentioned above, as the whole magnet switch 18 is moved to the back end side of motor 34, there is space between the front of the magnet switch 18 and the engine mounting portion, thereby setting a large range of rest positions for the pinion gear 15, improving starter installation, and allowing easy installation even on a vehicle with a torque converter. This invention has been described with reference to what are presently considered to be the most practical and preferred embodiments of the present invention. However, this invention is not meant to be limited to the disclosed embodiments, but rather is intended to cover all modifications and equivalent arrangements included within the scope of the appended claims.

Claims: Magnet switch (18) and a starter housing (1, 3, 8) for a starter motor (34) which includes an output shaft (5) and which is diposed in the starter housing (1,3,8), the starter housing (1, 3, 8) having an axial side end (3a) positioned axially opposite to the output shaft (5), said magnet switch (18) comprising movable and fixed contacts (23, 27) for controlling electric power supply to said starter motor (34); and wherein said fixed contact (27) includes a battery connecting terminal (27a), characterized in that the battery connecting terminal (27a) has a connecting seat surface which is located by a predetermined distance axially outwardly from an axial side end (3a) of said starter housing (1, 3, 8) and axially outwardly from a means for electrically connecting the magnet switch (18) and the starter motor (34) so that a battery cable (30) installed at the battery connecting terminal (27a) can be prevented from contacting with the starter motor (34) and the electrically connecting means. Magnet switch (18) and a starter housing (1, 3, 8) according to claim 1, wherein the starter housing (1,3,8) further has a magnetic switch cover (3c) on an axial side end (3b) of which the battery connecting terminal (27a) is located, and wherein the connecting seat surface located at the axial side end (3b) of the magnetic switch cover (3c) protrudes axially from said axial side end (3a) of said starter housing (1,3,8) by length L. Magnet switch (18) and a starter housing (1, 3, 8) according to claim 2, wherein said starter housing (1, 3, 8) includes a magnetic switch casing (1a) containing said magnetic switch (18), a motor casing (1b) containing said starter motor (34), and a starter cover (3) including the magnetic switch cover (3c). Starter for an internal combustion engine, said starter being connectable to a battery, said starter comprising: a starter housing (1,3,8); a starter motor (34) disposed in said housing (1,3,8); and a magnet switch (18) for transmitting electrical power from said battery to said starter motor (34) so as to start said engine, wherein said magnet switch (18) comprises a plunger (19), a drive shaft (22), and a moving contact (23) disposed at one end of said drive shaft (22), and includes a battery connecting terminal (27a) to which a battery cable connects, wherein said battery connecting terminal (27a) includes a first fixed contact (27) that transmits energy from said battery cable to said moving contact (23), characterized in that the battery connecting terminal (27a) has a connecting seat surface which protrudes axially outwardly by a predetermined distance from an axial side end (3a) of said starter housing (1, 3, 8) and which is located axially outwardly from a means for electrically connecting the magnet switch (18) and the starter motor (34) so that the battery cable (30)can be prevented from contacting with the starter motor (34) and the electrically connecting means. A starter as claimed in claim 4, wherein said starter housing (1, 3, 8) includes a magnetic switch casing (1a) containing said magnetic switch (18), a motor casing (1b) containing said starter motor (34), and a starter cover (3) having the axial side end (3a), and wherein said magnetic switch casing (1a) and said motor casing (1b) are formed of a first material and said starter cover (3) is formed of a second material. Starter according to claim 5, wherein said starter cover (3) includes a magnet switch cover (3c) which covers an opening portion of magnet switch casing (1a) and motor cover (3d) which covers an opening portion of motor casing (1b), wherein on an axial side end (3b) of the magnetic switch cover (3c) the battery connecting terminal (27a) is located, and wherein the connecting seat surface located at the axial side end (3b) of the magnetic switch cover (3c) protrudes axially from said axial side end (3a) of said starter cover (3) by length L. A starter according to claim 6, wherein said first fixed contact (27) includes a fastening means (31) for securing said battery cable to said switch cover (3c), and wherein said fastening means (31) is adapted to allow said battery cable (30) to be secured in any radial direction of a circle formed around said fastening means. A starter according to one of the claims 4 to 7, wherein said battery connecting terminal (27a) is connectable to a second fixed contact (28), wherein said starter motor (34) includes an armature (2), and wherein said second fixed contact (28) supplies electrical power to said armature (2) when said moving contact (23) contacts said first and second fixed contacts (27, 28). A starter according to claim 8, wherein a brush (4) of said starter motor (34) is directly connected to the second fixed contact (28) inside of the magnet switch (18). A starter according to claim 8, wherein the second fixed contact (28) is connected with a motor lead wire via a connecting terminal the axial side end thereof is provided axially inwardly from the connecting seat surface. A starter as claimed in claim 5, wherein said second material is non-magnetic material and said first material is magnetic material. Starter according to claim 5, wherein said switch casing (1a) and motor casing (1b) are made integrally of a magnetic material and said starter cover (3) is made of a heat resistant resin material. Starter according to claim 6, wherein said motor casing (1b) is disposed in parallel with said switch casing (1a).

Inventors: KAJINO SADAYOSHI, NIIMI MASAMI, KAJINO, SADAYOSHI, NIIMI, MASAMI
Applicants: DENSO CORP, DENSO CORPORATION
Application year: 1994
Main classification: H01H51
IPC codes: F02N15, H01H51